The invention relates to an apparatus for use in the manufacture of semiconductors, and more particularly, to a method and an apparatus for reuse of an abrasive fluid used in the manufacture of semiconductor devices.
A chemical-mechanical polishing (CMP) device is used in flattening a wafer surface in a semiconductor manufacturing step. The CMP device employs an abrasive slurry, and accordingly, as the quantity of products manufactured increases, the quantity of used abrasive slurry also increases. The quantity of abrasive slurry used influences the manufacturing cost, and hence an efficient reuse of the used abrasive slurry or fluid is required.
In the conventional practice of flattening a wafer surface, an abrasive slurry in liquid form which comprises a commercially available abrasive stock having a weight percentage of approximately 25 wt % and diluted by deionized water to nearly 13 wt % is used. Used abrasive fluid is further diluted within the polishing device to produce an effluent which may have a concentration on the order of about 0.1 to 0.2 wt %, for example. It will be understood that the abrasive effluent contains fragments of films abraded from the wafer and impurities produced by a polishing table (or pad) of the polishing device. Abrasive effluents are generally passed through a neutralization treatment before disposal or delivered to an industrial waste disposal undertaker in the form of sludges which result from a drainage treatment. The abrasive fluid represents a significant proportion of the wafer processing cost, but the abrasive effluent has been disposed of without a reuse thereof.
Abrasive grains contained in the abrasive effluent are agglomerated to larger sizes. However, a single grain in the agglomeration has a grain diameter which remains substantially unchanged from the grain size which it exhibited before it was fed to the polishing step, and thus retains a grain size which is still useable in the abrasive operation. Nevertheless, the grain agglomerations are disposed of without being recycled.
The cost of disposing sludges delivered to the industrial waste disposal undertaker adds to the semiconductor manufacturing cost. Thus, reuse of the abrasive effluent is of importance in reducing the semiconductor manufacturing cost.
It is an object of the invention to provide a method and an apparatus which allow reuse of an abrasive effluent.
In a first aspect of the present invention, a method is provided that reuses a slurry effluent containing agglomerations of abrasive grains which has been used in a polishing step in the manufacture of a semiconductor. First, the agglomerations of abrasive grains contained in the slurry effluent are crushed. Then, an abrasive fluid is regenerated using the slurry effluent containing the crushed abrasive grains.
In a second aspect of the present invention, an apparatus is provided that reuses a slurry effluent containing agglomerations of abrasive grains which has been used in a polishing step in the manufacture of a semiconductor. The apparatus includes a crusher for crushing the agglomerations of abrasive grains contained in the slurry effluent and a regeneration unit for regenerating an abrasive fluid using the slurry effluent containing the crushed abrasive grains.
In a third aspect of the present invention, a crusher is provided that crushes agglomerations of abrasive grains contained in a slurry effluent which has been used in the manufacture of a semiconductor. The crusher includes a tank for storing the slurry effluent and at least one of a mill, an ultrasonic oscillator and a pressurizing circulation unit attached to the tank.
In a fourth aspect of the present invention, an apparatus for concentrating a slurry effluent is provided. The apparatus includes a concentrating unit including a concentrating membrane for separating the slurry effluent into a concentrate fluid and a permeate fluid; a temperature regulator for adjusting the temperature of the slurry effluent; and a concentration controller for controlling the temperature regulator to control the concentration of the concentrate fluid.
In a fifth aspect of the present invention, an apparatus for regulating the quality of a slurry effluent including abrasive grains is provided. The apparatus includes a tank for storing the slurry effluent and a specific gravity adjusting unit for adjusting the concentration of the abrasive grains in the slurry effluent.
In a sixth aspect of the present invention, an apparatus for regulating the quality of a slurry effluent including abrasive grains is provided. The apparatus includes a tank for storing the slurry effluent and a pH adjusting unit for adjusting the pH of the slurry effluent.
In a seventh aspect of the present invention, an apparatus for cleansing a concentrating membrane used in concentrating a slurry effluent is provided. A concentrate fluid and a permeate fluid are generated by concentrating the slurry effluent. The apparatus includes a chamber for temporarily storing the permeate fluid and a back washing unit for cleansing the concentrating membrane using the permeate fluid stored in the chamber.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.